1. Field of Invention
This invention relates to the removal of living tissues or cells from a body for histological or cytological examination and more particularly to an improved method and apparatus for performing the same.
2. Description of the Related Art
In the United States, cancer is the second most common cause of death, accounting for about one fifth of the total. It has been found that early diagnosis is an important factor in successful treatment of the disease. There are a number of methods for examining suspicious tumors such as X-ray photography, ultrasound imaging and chemical analysis of bodily fluids. However, microscopic examination of the suspect tissue is the most accurate and efficient means of determining malignancy for most tumors.
Microscopic examination for the diagnosis of cancer and other diseases requires that a sample of suspected tissues be removed from the body. When a tumor is close to the surface of the body, this may be done by excising a small portion with a knife or scalpel. However, the excising procedure is not suitable for tumors that are beneath the surface of the body. These tumors are difficult to access and may require general anesthesia to be administered to the patient. Furthermore, the excision procedure usually produces significant trauma to the surrounding tissue and may result in a visible scar which would be undesirable on some portions of the body.
To provide an alternative to the excision procedure, a number of alternative techniques and devices have been developed for performing biopsies. One of these is a needle biopsy which uses a hollow needle and a syringe. The needle is inserted into the body so that the tip is placed inside the target tissue. The plunger of the syringe is then withdrawn to create low pressure. When the device works as intended, tissue is drawn into the needle and the device may then be withdrawn from the body.
One of the disadvantages of the needle biopsy is that it causes trauma to the body tissue and discomfort to the patient. As the plunger of the syringe is withdrawn, tissue is torn from its position in the body and sucked into the needle. The negative pressure created by withdrawing the syringe does not cleanly sever the sample tissue from the surrounding tissue and no cutting surface is provided for severing the tissue. More tissue is torn when the needle is withdrawn from the body. This tearing causes trauma to the surrounding tissue which usually causes pain to the patient during and after the procedure. Even if a local anesthetic is administered to the patient, the trauma may cause some amount of discomfort to the patient during the procedure and a significant amount of discomfort when the anesthetic has worn off.
Another disadvantage of the needle biopsy is that it does not always produce an adequate sample of the target tissue. As the needle is inserted into the body, some amount of non-target tissue is cut from the body along the path of the needle and lodged in the needle's tip. Furthermore, as the plunger of the syringe is withdrawn, some amount of non-target tissue may be drawn into the needle. This unwanted non-target tissue may effect the results of the tissue analysis.
Other needle biopsy devices utilize a design having a needle within a needle. Both needles are inserted into the body and the tip of the outer needle is usually inserted farther into the body than the inner needle thereby creating an internal cavity where tissue is intended to be captured. The outer needle is sometimes driven past the inner needle with the use of a spring activated mechanism. Devices that use spring activated mechanisms are sometimes called punch biopsy devices. When the device works as intended, the needles are withdrawn after the spring mechanism is activated and target tissue is torn from the body.
However, double needle devices and spring activated mechanisms inflict a significant amount of trauma to the patient. This trauma is especially undesirable for elderly patients and patients with hemophilia. In addition, double needle and spring activated biopsy devices produce poor samples. The samples tend to be non-uniform and jagged because of the traumatic way in which samples are retrieved and these samples may fail to retrieve an adequate sample of the target tissue.